High energy nanosecond pulsed fiber laser based on incoherent beam combination

Abstract

An incoherent beam combination based high energy nanosecond pulsed fiber laser includes a nanosecond pulsed seed, a fiber splitter, fiber amplifiers, synchronization fibers, a fiber laser combiner and a laser output head. The output fiber of the pulsed seed is fusion spliced to the input fiber of the splitter; the output fibers of the splitter are fusion spliced to the fiber amplifiers separately; synchronization fibers are fusion spliced between the amplifiers and the input fibers of the fiber laser combiner. The nanosecond pulsed seed is split by the fiber splitter and amplified in the later fiber amplifiers; synchronization fibers make sure the optical time-domain synchronization; the fiber laser combiner allows for the incoherent combination of high energy pulsed laser.

We claim: 
     
       1. An incoherent beam combination based nanosecond pulsed fiber laser, comprising: a nanosecond pulsed seed, a fiber splitter, fiber amplifiers, synchronization fibers, a fiber laser combiner and a laser output head; wherein an output fiber of the pulsed seed is fusion spliced to the input fiber of the splitter; output fibers of the splitter are fusion spliced to the fiber amplifiers separately; synchronization fibers are fusion spliced between the amplifiers and an input fibers of the fiber laser combiner; the nanosecond pulsed seed is split by the fiber splitter and amplified in the later fiber amplifiers; synchronization fibers are configured for optical time-domain synchronization; and the fiber laser combiner allows the incoherent combination of high energy pulsed laser. 
     
     
       2. The fiber laser of  claim 1 , wherein said nanosecond pulsed seed is an actively Q-switch fiber laser, including a pump diode, a signal pump fiber combiner, double cladding Yb +  doped fiber, high-reflection (HR) fiber grating, fiber coupled acousto-optic modulator (AOM), partial-reflection (PR) fiber grating and fiber optic isolator, the pump diode is fusion spliced with the pump fiber of the combiner; a signal fiber of the combiner is cleaved with an 8° angle; an output fiber of the combiner is fusion spliced with the HR fiber grating; a port fiber of the HR fiber grating is fusion spliced with the double cladding Yb +  doped fiber; the AOM is fusion spliced between the double cladding Yb +  doped fiber and the PR fiber grating; an input fiber of the isolator is fusion spliced with the PR fiber grating; and an output fiber of the isolator acts as the output of the nanosecond pulsed seed. 
     
     
       3. The fiber laser of  claim 1 , wherein the nanosecond pulsed seed is an electric current modulated diode laser including pulsed electric current driver, fiber coupled electric current modulated diode and a fiber optic isolator; the diode laser is modulated by the driver and outputs pulsed laser with a repetition rate from thousands hertz to hundreds hertz and a pulse width from tens nanosecond to hundreds nanosecond; the input fiber of the isolator is fusion spliced with the diode laser and the output fiber acts as the output fiber of the nanosecond pulsed seed. 
     
     
       4. The fiber laser of  claim 1 , wherein the nanosecond pulsed seed is a fiber coupled gain-switched semiconductor laser or other lasers which could supply nanosecond pulsed seed. 
     
     
       5. The fiber laser of  claim 1 , wherein the fiber amplifier comprises fiber amplifier stages which are forward pumped or backward pumped; the amplifier stage includes a signal pump combiner, a diode pump laser, double cladding Yb +  doped fiber and a fiber optic isolator; the output fiber of the diode pump laser is fusion spliced with the pump fiber of the signal pump combiner; the output fiber of the signal pump combiner is fusion spliced with the double cladding Yb +  doped fiber; and the other end of the double cladding Yb +  doped fiber is fusion spliced with the fiber optic isolator. 
     
     
       6. The fiber laser of  claim 1 , wherein the fiber amplifiers have more than two amplified stages which are used to get higher power and higher energy; the output fiber of the former amplified stage is fusion spliced with the signal fiber of later stage; the signal fibers of the first amplified stages are fusion spliced with the output fibers of the fiber splitter; and the output fibers of last amplified stages are fusion spliced with the synchronization fibers. 
     
     
       7. The fiber laser of  claim 1 , wherein the synchronization fibers are passive fiber; the time-domain synchronization is achieved by changing the length of the synchronization fibers. 
     
     
       8. The fiber laser of  claim 1 , wherein the fiber splitter is one single splitter or multi-splitter. 
     
     
       9. The fiber laser of  claim 1 , wherein the laser combiner are capable of combining N branches laser into one output fiber. 
     
     
       10. The fiber laser of  claim 1 , wherein the output head is cylindrical quartz, whose end face has an 8° and a wavelength-depended high transparency layer.